I'd argue both DMC and Castlevania has more depth than Duke. While DMC can be summed down to "Cocky man kicks ass", there's been greater depths explored with a lot of the cast. Not an ocean, of course, but there's more to the characters than mere face value.

Castlevania has a wide cast of characters who, while not always presented in the most complex manner, have implied histories and personalities that can be built upon. There's enough skeleton to support some good muscle.

Duke has the depth of a petri dish. He's the embodiment of "What You See Is What You Get".

Like I said elsewhere, a single movie in his peak, or a low budget tongue-in-cheek throwback, I could get behind.

I just don't see the potential of a Duke series, or even a film getting beyond cult classic status among a select few.